Eigensystem

Eigensystem[m] gives a list {values,vectors} of the eigenvalues and eigenvectors of the square matrix m. 

Eigensystem[{m,a}] gives the generalized eigenvalues and eigenvectors of m with respect to a. 

Eigensystem[m,k] gives the eigenvalues and eigenvectors for the first k eigenvalues of m. 

Eigensystem[{m,a},k] gives the first k generalized eigenvalues and eigenvectors.

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